I tried to compile librdkafka on OpenBSD 6.5 (clang 7.0.1) and clang compiled
the __thread parts with some built-in mechanism. I upgraded the system to
OpenBSD 6.9 and TLS is no longer supported by the in-tree clang. Was this
intended to be turned off? Did the 6.5 version even work? Is Thread Local
Storage support in clang desired in general or no? Marc Espie's clang
presentation from July 2017 mentions that we do and that Mark Kettenis
helped make it happen. I'm having a hard time finding much other discussion
either way.
